わけにはいかない is an expression used to state that one cannot do something due to social, moral, or situational pressures. It combines わけ, meaning 'reason' or 'circumstance', with the negative form of 'to go', 行(い)かない. This phrasing creates the sense of 'it's not possible to go down that path' or 'I am in a situation where I can't'. Common translations include 'I can't possibly (do A)' or 'I can't just (do A)'.

This grammar point attaches to the dictionary form (plain, non-past) of a verb. It is used to express that a certain action is not an option for the speaker, because it would be irresponsible, illogical, or go against common sense or social expectations.

• 明日(あした)は大事(だいじ)な試験(しけん)があるから、一日中(いちにちじゅう)遊(あそ)んでいるわけにはいかない。
  I have a big test tomorrow, so I can't afford to spend the whole day playing.
• 友達(ともだち)から聞(き)いた秘密(ひみつ)だから、他(ほか)の人(ひと)に話(はな)すわけにはいかない。
  It's a secret my friend told me, so there's no way I can tell other people.

While わけにはいかない often implies that an action is wrong or shouldn't be done, it can also be used for something the speaker wants to do but cannot due to external circumstances. The specific nuance between 'I shouldn't' and 'I can't' is understood from the context of the situation.

• このケーキはとても美味(おい)しそうだけど、ダイエット中(ちゅう)だから食(た)べるわけにはいかない。
  This cake looks so delicious, but since I'm on a diet, I just can't eat it.
• 明日(あした)の朝(あさ)は早(はや)いから、遅(おそ)くまで飲(の)むわけにはいかない。
  I have to be up early tomorrow morning, so I can't possibly stay out drinking late.

When used in this way, the phrase often carries a feeling of resignation or regret, similar to saying in English, 'as much as I'd like to, I just can't'.